Process for presulfiding hydrocarbon processing catalysts

ABSTRACT

The present invention relates to a process for presulfiding hydrocarbon processing catalysts by impregnating the catalyst with an inorganic polysulfide solution such that at least a portion of said sulfide or sulfur is incorporated in the pores of said catalyst, and thereafter heating the sulfur-incorporated catalyst under non-oxidizing conditions to fix the incorporated sulfur onto the catalyst.

FIELD OF THE INVENTION

This invention relates to a method of presulfiding hydrocarbonprocessing catalysts and catalyst compositions resulting from suchtreatment.

BACKGROUND OF THE INVENTION

It is well known that it is often desirable to employ the step of"presulfiding" or "presulfurizing" of the metals forming part of thecomposition of certain catalysts for refining and/or hydroconvertinghydrocarbons, either before they are used initially, i.e., freshcatalysts, or before they are re-used following regeneration.Hydrocarbon processing catalysts, such as hydrotreating, hydrocrackingand tail-gas treating catalysts are typically subjected to such a"presulfiding step".

A hydrotreating catalyst may be defined as any catalyst compositionwhich may be employed to catalyze the hydrogenation of hydrocarbonfeedstocks, and most particularly to hydrogenate particular componentsof the feed stock, such as sulfur-, nitrogen- and metals-containingorgano-compounds and unsaturates. A hydrocracking catalyst may bedefined as any catalyst composition which may be employed to crack largeand complex petroleum derived molecules to attain smaller molecules withthe concomitant addition of hydrogen to the molecules. A tail gascatalyst may be defined as any catalyst which may be employed tocatalyze the conversion of hazardous effluent gas streams to lessharmful products, and most particularly to convert oxides of sulfur tohydrogen sulfide which can be recovered and readily converted toelemental sulfur. A reduced catalyst may be defined as any catalyst thatcontains a metal in the reduced state such as, for example, an olefinhydrogenation catalyst. Such metals are typically reduced with areducing agent such as, for example, hydrogen or formic acid. The metalson these reduced catalyst may be fully reduced or partially reduced.

Catalyst compositions for hydrogenation catalysts are well known andseveral are commercially available. Typically, the active phase of thecatalyst is base on at least one metal of group VIII, VIB, IVB, IIB orIB of the Periodic Table of the Elements. In general, the hydrogenationcatalysts contains at least one element selected from Pt, Pd, Ru, Ir,Rh, Os, Fe, Co, Ni, Cu, Mo, W, Ti Hg, Ag or Au supported usually on asupport such as alumina, silica, silica-alumina and carbon.

Catalyst compositions for hydrotreating and/or hydrocracking or tail gastreating are well known and several are commercially available. Metaloxide catalysts which come within this definition includecobalt-molybdenum, nickel-tungsten, and nickel-molybdenum supportedusually on alumina, silica and silica-alumina, including zeolite,carriers. Also, other transition metal element catalysts may be employedfor these purposes. In general, catalysts containing at least oneelement selected from V, Cr, Mn, Re, Co, Ni, Cu, Zn, Mo, W, Rh, Ru, Os,Ir, Pd, Pt, Ag, Au, Cd, Sn, Sb, Bi and Te have been disclosed assuitable for these purposes.

For maximum effectiveness these metal oxide catalysts are converted atleast in part to metal sulfides. The metal oxide catalysts can besulfided in the reactor by contact at elevated temperatures withhydrogen sulfide or a sulfur-containing oil or feed stock ("in-situ").

However, it is advantageous to the user to be supplied with metal oxidecatalysts having sulfur, as an element or in the form of anorgano-sulfur compound, incorporated therein. These presulfurizedcatalysts can be loaded into a reactor and brought up to reactionconditions in the presence of hydrogen causing the sulfur or sulfurcompound to react with hydrogen and the metal oxides thereby convertingthem into sulfides without any additional process steps being needed.These presulfurized catalysts provide an economic advantage to the plantoperator and avoid many of the hazards such as flammability andtoxicity, which the plant operator encounter when using hydrogensulfide, liquid sulfides, organic polysulfides and/or mercaptans tosulfide the catalysts.

Several methods of presulfurizing metal oxide catalysts are known.Hydrotreating catalysts have been presulfurized by incorporating sulfurcompounds into a porous catalyst prior to hydrotreating a hydrocarbonfeedstock. For example, U.S. Pat. No. 4,530,917 discloses a method ofpresulfurizing a hydrotreating catalyst with organic polysulfides. U.S.Pat. No. 4,177,136 discloses a method of presulfurizing a catalyst bytreating the catalyst with elemental sulfur. Hydrogen is then used as areducing agent to convert the elemental sulfur to hydrogen sulfide insitu. U.S. Pat. No. 4,089,930 discloses the pretreatment of a catalystwith elemental sulfur in the presence of hydrogen. U.S. Pat. No.4,943,547 discloses a method of presulfurizing a hydrotreating catalystby subliming elemental sulfur into the pores of the catalyst thenheating the sulfur-catalyst mixture to a temperature above the meltingpoint of sulfur in the presence of hydrogen. The catalyst is activatedwith hydrogen. PCT specification WO 93/02793 discloses a method ofpresulfurizing a catalyst where elemental sulfur is incorporated in aporous catalyst and at the same time or subsequently treating thecatalyst with a liquid olefinic hydrocarbon.

However, these ex-situ presulfurized catalysts must be subjected to aseparate activation step prior to contact with the hydrocarbon feed in ahydrocarbon processing reactor.

Therefore, it is an object of the present invention to prepare anactivated, presulfurized or presulfided catalyst, either fresh orregenerated, without the requirement for a separate activation treatmentprior to contact with the hydrocarbon feed in the reactor.

SUMMARY OF THE INVENTION

The present invention relates to a method of presulfurizing a sulfidablemetal oxide(s)-containing catalyst. According to the invention, there isprovided a method of presulfurizing porous particles of a sulfidablecatalyst containing at least one metal or metal oxide, which comprises:

(a) contacting said catalyst with an inorganic polysulfide solution at atemperature such that at least a portion of said sulfide or sulfur isincorporated in the pores of said catalyst; and

(b) heating said impregnated, sulfur-incorporated catalyst undernon-oxidizing conditions such that said incorporated sulfide or sulfuris fixed onto the catalyst.

The method is particularly suitable for application to hydrotreatingand/or hydrocracking or tail gas treating catalysts.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a process for presulfiding hydrocarbonprocessing catalysts by impregnating the catalyst with an inorganicpolysulfide solution such that at least a portion of said sulfide orsulfur compound is incorporated in the pores of said catalyst, andthereafter heating the impregnated catalyst under non-oxidizingconditions to fix the incorporated sulfur onto the catalyst.

As used in this specification, the term "inorganic polysulfide" refersto polysulfide ions having the general formula S.sub.(x)²⁻ where x isgreater than 2, preferably from about 3 to about 9, and more preferablyfrom about 3 to about 5, and the "inorganic" terminology, in thiscontext refers to the nature of the polysulfide moiety rather to thecounterion, which may be organic. As used herein, the term "inorganicpolysulfide solution" refers to a solution containing inorganicpolysulfides. As used in this specification, the terms "metal(s)-","metal oxide(s)-" and "metal sulfide(s)-" containing catalysts includecatalyst precursors that are subsequently used as actual catalysts.Further, the term "metal(s)" includes metal(s) in partially oxidizedform. The term "metal oxide(s)" includes metal oxide(s) in partiallyreduced form. The term "metal sulfide(s)" includes metal sulfide(s) thatare partially sulfided as well as totally sulfided metals. The aboveterms include in part other components such as carbides, borides,nitrides, oxyhalides, alkoxides and alcoholates.

In the present invention, a presulfidable metal- or metaloxide-containing catalyst is contacted with an inorganic polysulfidesolution to presulfurizing the presulfidable metal or metal oxidecatalysts at a temperature and for a time effective to causeincorporation of the sulfide or sulfur into the pores of the catalysts.The catalyst is heated following impregnation under non-oxidizingconditions for a time sufficient to fix the incorporated sulfide orsulfur onto the catalyst.

The catalysts referred to herein as "sulfidable metal oxide catalyst(s)"can be catalyst precursors that are used as actual catalysts while inthe sulfided form and not in the oxide form. While reference is made tometal oxide catalyst(s), it is understood that while the normal catalystpreparative techniques will produce metal oxide(s), it is possible toutilize special preparative techniques to produce the catalytic metalsin a reduced form, such as the zero valent state. Since metals in thezero valent state will be sulfided as well as the oxides when subjectedto sulfiding conditions, catalysts containing such sulfidable metalseven in reduced or zero valent states will be considered for thepurposes of this invention as sulfidable metal oxide catalyst(s).Further, since the preparative technique of the instant invention can beapplied to regenerated catalysts which may have the metal sulfide notcompletely converted to the oxides, "sulfidable metal oxide catalyst(s)"also refers to these catalysts which have part of their metals in thesulfided state.

In a preferred embodiment, prior to impregnation with the inorganicpolysulfide solution, the metal oxide catalyst particles or pellets arehydrated to equilibrium with air in order to reduce the initialexotherm.

In carrying out the process of the present invention, porous catalystparticles are contacted and reacted with an inorganic polysulfidesolution under conditions which cause the sulfide or sulfur compounds tobe incorporated into the pores of the catalyst by impregnation. Theinorganic polysulfide-incorporated or sulfur compound-incorporatedcatalysts will be referred to as "sulfur-incorporated catalysts."

The inorganic polysulfide solution is typically prepared by dissolvingelemental sulfur in an aqueous ammonium (or ammonium derivative, i.e.,tetramethyl ammonium, tetraethyl ammonium, etc.) sulfide solution.Preferred polysulfides include inorganic polysulfides of general formulaS.sub.(x)²⁻ wherein x is an integer greater than 2, preferably from 3 to9 and more preferably from 3 to 5, such as, for example, S.sub.(3)²⁻,S.sub.(4)²⁻, S.sub.(5)²⁻, S.sub.(6)²⁻ and the like, and mixturesthereof.

The inorganic polysulfide solution is a red solution in which a darkcoloring denotes a long chain polysulfide and a lighter coloring denotesa shorter chain polysulfide. The inorganic polysulfide solution thusprepared is used to impregnate the catalyst particles using a porevolume impregnation method or by incipient wetness such that the poresof the catalyst are filled without exceeding the volume of the catalyst.The amounts of sulfur used in the instant process will depend upon theamounts of catalytic metal present in the catalyst that needs to beconverted to the sulfide. For example, a catalyst containing molybdenumwould require two moles of sulfur or mono-sulfur compounds to converteach mole of molybdenum to molybdenum disulfide, with similardeterminations being made for other metals. On regenerated catalysts,existing sulfur levels may be factored into the calculations for theamounts of sulfur required.

The amount of sulfur typically present in the inorganic polysulfidesolution in the present process is in the range of from about 5 percentby weight to about 50 percent by weight, basis the total weight of thesolution. Higher concentrations of sulfur can be obtained by increasingthe concentration of the starting ammonium sulfide solution. Theinorganic polysulfide solution will generally have a ratio of sulfur tosulfide by weight ranging from about 2:1 to about 5:1, and preferably inthe range of from about 2:1 to about 3:1. The amount of sulfur in theinorganic polysulfide solution is generally such that the amount ofsulfur impregnated onto the catalysts particles is typically an amountsufficient to provide for stoichiometric conversion of the metalcomponents from the oxide form to the sulfide form and is generally inthe range of from about 2 percent by weight to about 15 percent byweight, and preferably from about 4 percent by weight to about 12percent by weight, basis the total weight of the sulfurized catalyst.

It has been found that the addition of presulfurizing sulfur in amountsdown to about 50 percent of the stoichiometric requirement results incatalysts having adequate hydrodenitrification activity, which is animportant property of hydrotreating and first stage hydrocrackingcatalysts. Thus, the amount of presulfurizing sulfur used forincorporation into the catalyst will typically range from about 0.2 toabout 1.5 times the stoichiometric amount, and preferably from about 0.4to about 1.2 times the stoichiometric amount.

For hydrotreating/hydrocracking and tail gas treating catalystscontaining Group VIB and/or Group VIII metals the amount ofpresulfurizing sulfur employed is typically about 1% to about 15% byweight of the catalyst charged, and preferably, the amount ofpresulfurizing sulfur employed is about 4% to about 12% by weight of thecatalyst charged.

The sulfur impregnation step will typically be carried out at atemperature ranging from about 0° C. to about 30° C. or higher, up toabout 60° C. The lower temperature limit is fixed by the freezing pointof the inorganic polysulfide solution under the specific conditions ofimpregnation, whereas the upper temperature limit is fixed primarily bydecomposition of the inorganic polysulfide solution to volatilecompounds and elemental sulfur.

Following impregnation of the catalyst particles with the inorganicpolysulfide solution, the sulfur-incorporated catalyst is subjected to aheat treatment in the presence of a flowing non-oxidizing gas such as,for example, nitrogen, carbon dioxide, argon, helium and the like, at atemperature sufficient to drive out most of the residual pore volumewater and to fix the sulfur on the catalyst. The heat treatment of thesulfur-incorporated catalyst is preferably carried out using a rampedtemperature procedure in which the sulfur-incorporated catalysts arefirst heated to a temperature in the range of from about 50° C. to about150° C., preferably about 120° C., to drive out most of the pore volumewater. The catalysts were then ramped to a final hold temperature in therange of from about 120° C. to about 400° C., and preferably from about230° C. to about 350° C., to fix the incorporated sulfur onto thecatalyst. Following this heat treatment, the catalysts were cooled toroom temperature and rehydrated with a water saturated non-oxidizinggas. The resulting catalysts are stable to handling in air.

The presulfurized or presulfided catalyst of the instant invention isthen loaded into a hydrotreating and/or hydrocracking reactor or tailgas reactor, the reactor is heated up to operating (hydrotreating and/orhydrocracking or tail gas treating) conditions, and the catalyst is thenimmediately contacted with the hydrocarbon feedstock, without the needfor an extended activation of the catalyst with hydrogen prior tocontact of the catalyst with the hydrocarbon feedstock. While notwishing to be bound by any particular theory, it is believed that theextended activation period with hydrogen generally required for ex-situpresulfided catalysts is not necessary for catalysts presulfidedaccording to the present invention because, in the present process, mostof the sulfur has already reacted with the metal oxides to form metalsulfides, or alternatively, the sulfur is fixed in the pores of thecatalyst to such an extent that it doesn't leave the pores of thecatalyst prior to being converted to the sulfide.

The process of the present invention is further applicable to thesulfurizing of spent catalysts which have been oxy-regenerated. After aconventional oxy-regeneration process, an oxy-regenerated catalyst maybe presulfurized as would fresh catalyst in the manner set forth above.

The present process is particularly suitable for application tohydrotreating and/or hydrocracking or tail gas treating catalysts. Thesecatalysts typically comprise Group VIB and/or Group VIII metalssupported on porous supports such as alumina, silica, silica-alumina,zeolite and the like. The materials are well defined in the art and canbe prepared by techniques described therein, such as in U.S. Pat. No.4,530,911, and U.S. Pat. No. 4,520,128, both incorporated by referenceherein. Preferred hydrotreating and/or hydrocracking or tail gastreating catalysts will contain a group VIB metal selected frommolybdenum, tungsten and mixtures thereof and a Group VIII metalselected from nickel, cobalt and mixtures thereof supported on alumina.Versatile hydrotreating and/or hydrocracking catalysts which show goodactivity under various reactor conditions are alumina-supportednickel-molybdenum and cobalt-molybdenum catalysts. Phosphorous issometimes added as a promoter. A versatile tail gas treating catalystwhich shows good activity under various reactor conditions is analumina-supported cobalt-molybdenum catalyst.

The ex-situ presulfurization method of this invention allows thehydrotreating, hydrocracking and/or tail gas treating reactors to bestarted up more quickly by providing for immediate contact with thehydrocarbon feedstock in the reactor and eliminating the extendedactivation step with hydrogen which is necessary for conventionalex-situ presulfurized catalysts.

Thus, the instant invention relates to an improved hydrotreating and/orhydrocracking process which comprises contacting at hydrotreating and/orhydrocracking conditions a hydrocarbon feedstock and hydrogen with acatalyst which has been presulfurized according to the methods taughtherein and which has been heated to hydrotreating and/or hydrocrackingtemperature in the presence of a hydrocarbon feedstock.

Hydrotreating conditions comprise temperatures ranging from about 100°C. to about 425° C., pressures above about 40 atmospheres. The totalpressure will typically range from about 400 to about 2500 psig. Thehydrogen partial pressure will typically range from about 200 to about2200 psig. The hydrogen feed rate will typically range from about 200 toabout 10000 standard cubic feet per barrel ("SCF/BBL"). The feedstockrate will typically have a liquid hourly space velocity ("LHSV") rangingfrom 0.1 to about 15.

Hydrocracking conditions comprise temperatures ranging from about 200°C. to about 500° C., pressures above about 40 atmospheres. The totalpressure will typically range from about 400 to about 3000 psig. Thehydrogen partial pressure will typically range from about 300 to about2600 psig. The hydrogen feed rate will typically range from about 1000to about 10,000 standard cubic feet per barrel ("SCF/BBL"). Thefeedstock rate will typically have a liquid hourly space velocity("LHSV") ranging from 0.1 to about 15. First stage hydrocrackers, whichcarry out considerable hydrotreating of the feedstock may operate athigher temperatures than hydrotreaters and at lower temperatures thansecond stage hydrocrackers.

Tail gas treatment reactors typically operate at temperatures rangingfrom about 200° C. to about 400° C. and at atmospheric pressure. About0.5-5% vol. of the tail gas fed to the reactor will comprise hydrogen.Standard gaseous hourly space velocities of the tail gas through thereactor will range from about 500 to about 10,000 hr⁻¹. There areseveral ways the subject catalysts can be started up in a tail gastreatment reactor. Claus unit feed or tail gas can be used to start upthe subject catalysts. Supplemental hydrogen, as required, may beprovided by a gas burner operating at a substoichiometric ratio in orderto produce hydrogen.

The ranges and limitations provided in the instant specification andclaims are those which are believed to particularly point out anddistinctly claim the instant invention. It is, however, understood thatother ranges and limitations that perform substantially the samefunction in substantially the same way to obtain the same orsubstantially the same result are intended to be within the scope of theinstant invention as defined by the instant specification and claims.

The invention will be described by the following examples which areprovided for illustrative purposes and are not to be construed aslimiting the invention.

ILLUSTRATIVE EMBODIMENTS Preparation of Inorganic Polysulfide Solution

An inorganic polysulfide solution for use in the following examples wasprepared by adding 42 grams of elemental sulfur to a vigorously stirredsolution of ammonium sulfide (150 milliliters, 22% wt.). The elementalsulfur immediately began to dissolve and the resulting solution becamered-orange. The mixture was stirred until all of the sulfur wasdissolved. The actual sulfur content of the solution was 30% wt, and thesulfur to sulfide ratio in the solution was 3.0.

EXAMPLE 1

A commercial hydrotreating catalyst having the properties listed belowwas used to prepare the sulfurized catalysts.

                  TABLE A                                                         ______________________________________                                        Catalyst Properties                                                           ______________________________________                                        Nickel              3.0% wt                                                   Molybdenum          13.0% wt                                                  Phosphorous         3.5% wt                                                   Support             gamma alumina                                             Surface Area, m.sup.2 /g                                                                          162                                                       Water Pore Vol., cc/g                                                                             0.47                                                      Size                1/16 inch trilobes                                        ______________________________________                                    

A 50 gram sample of the above catalyst was hydrated to equilibrium withair. The hydrated catalyst was then impregnated with 28.0 milliliters ofthe above inorganic polysulfide solution. This solution was addeddropwise to an agitated bed of catalyst pellets contained in a nitrogenpurged (0.5 liters/minute) three hundred milliliter 3N round bottomedflask, using a syringe pump apparatus. The stand on which the roundbottomed flask was attached was vibrated using an FMC vibrating table,with the amplitude of vibration set so as to create a tumbling bed ofcatalyst pellets. The resulting black pellets were then heated from roomtemperature to 121° C. (250° F.) for one hour. The catalyst was thenramped to the final hold temperature of 260° C. (500° F.) and held forone hour. The final sulfur level was about 9.3% by weight of the totalcatalyst. The sulfur content of the catalyst were analyzed using LECOcorporation SC-432 carbon-sulfur analyzer. The properties of thecatalyst are listed in Table 1 below.

Comparative Example A

The commercial hydrotreating catalyst described in Example 1 above wassubjected to the following in-situ sulfiding procedure.

A sample of the catalyst was crushed and sieved to 15-45 loaded into atesting unit having a set pressure of sulfiding gas (5% H₂ S/95% H₂) of1 atmosphere and a flow rate 45 liters/hour. The temperature is thenramped from room temperature up to 204° C. at 0.5° C. per minute andheld at that temperature for two hours. The temperature is thenincreased to 371° C. at a rates of 0.5° C. per minute and held at thattemperature for one hour and then cooled to room temperature.Thereafter, the unit is switched to a pure hydrogen flow and targetrates and pressures are established, and then hydrocarbon feed isintroduced. The final sulfur level was about 10% by weight of the totalcatalyst. The sulfur content of the catalyst were analyzed using LECOcorporation SC-432 carbon-sulfur analyzer. The properties of thecatalyst are listed in Table 1 below.

Catalyst Testing

The catalyst sulfided in Example 1 above was used to hydrotreat acatalytically-cracked heavy gas oil (CCHGO) in a trickle-flow reactor. Asample of the catalyst was crushed and sieved to a 16-45 mesh, dilutedwith silicon carbide and loaded into a trickle-flow reactor tube. Thereactor tube was pressured to 1100 psig with hydrogen at a flow rate of45 liters per hour. The reactor was then heated to 93° C. and a CCHGOfeed was passed over the catalyst at a liquid hourly space velocity(LHSV) of 1.5. The temperature was ramped at a rate of 0.5° C. per hourup to 332° C. and then held for a period of sixty hours. Samples werethen collected and analyzed to determine the hydrogenation,hydrodenitrification and hydrosulfurization activities. Rate constantsare reported relative to Comparative Example A.

Comparative Example A was tested in a manner similar to Example 1 above,except that since the catalyst was sulfided by an in-situ sulfidingmethod, the catalyst was not unloaded from the reactor followingsulfiding.

The results are presented in Table 1 below.

As can be seen in Table 1, a presulfiding method according to theinvention which utilizes an inorganic polysulfide solution is aneffective means for incorporating sulfur into a hydrotreating catalyst(Example 1).

                  TABLE 1                                                         ______________________________________                                                       Heat                                                                 Sulfur   Temp   wt %  Sulfur                                            Ex. # Source   °C.                                                                           Sulfur                                                                              Reten..sup.1                                                                        Hydro.sup.2                                                                         HDS.sup.2                                                                          HDN.sup.2                        ______________________________________                                        1     Inorganic                                                                              121    9.3   90%   0.89  0.72 0.86                                   Poly-                                                                         sulfide                                                                 Comp. 5%       371    8.8   NM    1.0   1.0  1.0                              Ex. A H.sub.2 S/H.sub.2                                                       ______________________________________                                         NM = Not Measured                                                             .sup.1 Reported as % of sulfur remaining relative to sulfur loaded onto       catalyst                                                                      .sup.2 Relative to H.sub.2 S/H.sub.2 sulfided catalyst                   

EXAMPLE 2

Z-763 Ni-W/Ultrastable Y zeolite based hydrocracking catalyst, availablefrom Zeolyst International Inc., was presulfurized according to theprocedure set forth below.

A 100 gram sample of the above catalyst was hydrated to equilibrium withair. The hydrated catalyst was then impregnated with 23.4 milliliters ofthe above inorganic polysulfide solution diluted to the water porevolume of 38.6 milliliters. This solution was added dropwise to anagitated bed of catalyst pellets contained in a nitrogen purged (0.5liters/minute) three hundred milliliter 3N round bottomed flask, using asyringe pump apparatus. The stand on which the round bottomed flask wasattached was vibrated using an FMC vibrating table, with the amplitudeof vibration set so as to create a tumbling bed of catalyst pellets. Theresulting black pellets were then heated from room temperature to 150°C. for one hour. The catalyst was then ramped to the final holdtemperature of 343° C. and held for one hour. After cooling to roomtemperature, the air sensitive catalyst was rehydrated with water usinga water saturated nitrogen stream so that the catalyst can be safelyhandled in air for reactor loading. The final sulfur level was about 8%by weight of the total catalyst. The sulfur content of the catalyst wereanalyzed using LECO corporation SC-432 carbon-sulfur analyzer. Theproperties of the catalyst are listed in Table 2 below.

Comparative Example B

The commercial hydrocracking catalyst described in Example 2 above wassubjected to the following in-situ sulfiding procedure.

A sample of the catalyst was loaded into a testing unit having a setpressure of sulfiding gas (5% H₂ S/95% H₂) of 350 psig and a flow rateset to give a gas hourly space velocity (GHSV) of 1500 (e.g., for 40 ccsof catalyst, the flow rate is 60 liters/hour). The temperature is thenramped from room temperature up to 150° C. in one-half hour and thenfrom 150° C. to 370° C. over a six hour period. The temperature is thenheld at 370° C. for two hours and then lowered to 150° C. Thereafter,the unit is switched to a pure hydrogen flow and target rates andpressures are established, and then hydrocarbon feed is introduced. Thefinal sulfur level was about 5.5% by weight of the total catalyst. Thesulfur content of the catalyst were analyzed using LECO corporationSC-432 carbon-sulfur analyzer. The properties of the catalyst are listedin Table 2 below.

Catalyst Testing

The catalysts sulfided in Example 2 and Comparative Example B above wereused to hydrocrack a hydrotreated catalytically-cracked light gas oil ina trickle-flow reactor. A sample of the catalyst was crushed and sievedto a 16-45 mesh, diluted with silicon carbide and loaded into atrickle-flow reactor tube. The reactor tube was pressured to 1500 psigwith hydrogen. The reactor was then heated to 150° C. and a hydrotreatedcatalytically-cracked light gas oil feed was passed over the catalyst ata liquid hourly space velocity (LHSV) of 6.0. The hydrogen to feed ratioin the reactor tube was 6500 standard cubic feet per barrel (SCF/BBL).The temperature was ramped at a rate of 22° C. per day for four days andat a rate of 6° C. per day for five days up to a temperature of 260° C.The temperature was then adjusted to obtain a target conversion of 12 wt% of 190+° C. in feed. The results are presented in Table 2 below.

                                      TABLE 2                                     __________________________________________________________________________              Heat                       Temp.                                        Sulfur                                                                              Temp                                                                             wt %                                                                              Normalized     Sulfur                                                                             Req'd                                    Ex. #                                                                             Source                                                                              °C.                                                                       Sulfur                                                                            Sulfur.sup.1                                                                        Carbon                                                                            Hydrogen                                                                           Retention.sup.2                                                                    (°C.).sup.3                       __________________________________________________________________________    2   Inorganic                                                                           343                                                                              7.48                                                                              7.48  NM  NM   96%  348                                          Polysulfide                                                               Comp.                                                                             5% H.sub.2 S/H.sub.2                                                                371                                                                              5.45                                                                              5.45  NM  NM   --   348                                      Ex. B                                                                         __________________________________________________________________________     NM = Not Measured                                                             .sup.1 Normalized Sulfur = Analyzed Sulfur/(100 - (wt % C + wt % H))          × 100                                                                   .sup.2 Reported as % of sulfur remaining relative to sulfur loaded onto       catalyst                                                                      .sup.3 Temperature required for target hydrocracking conversion. Target       conversion is 12 wt % of 190+° C. (375+° F.) in feed.      

As can be seen in Table 2, the sulfur retention of a catalystpresulfided according to the invention, in which an inorganicpolysulfide solution is utilized (Example 2), is 96%, indicating thatessentially all of the sulfur remains on the catalyst after the heatingstep. In addition, the hydrocracking activity of the catalyst in Example2 is equivalent to that of a hydrocracking catalyst presulfided using aconventional in-situ presulfiding method (Comparative Example 2).

What is claimed is:
 1. A process for presulfurizing porous particles ofa sulfidable catalyst containing at least one metal or metal oxide,which comprises;(a) impregnating said catalyst with an inorganicpolysulfide solution such that at least a portion of said sulfide orsulfur is incorporated in the pores of said catalyst; and (b) heatingsaid sulfur-incorporated catalyst in the presence of a non-oxidizingatmosphere.
 2. The process of claim 1 wherein said inorganic polysulfidesolution contains polysulfide ions having the general formulaS.sub.(x)²⁻ where x is greater than
 2. 3. The process of claim 1 whereinsaid inorganic polysulfide solution is prepared by dissolving elementalsulfur in an aqueous ammonium or ammonium derivative sulfide solution.4. The process of claim 1 wherein said inorganic polysulfide solutioncontains an amount of sulfur in the range of from about 5 percent byweight to about 50 percent by weight, basis the total weight of thesolution.
 5. The process of claim 1 wherein, prior to step a), saidcatalyst containing at least one metal oxide is hydrated to equilibriumwith air.
 6. The process of claim 1 wherein said impregnation in step a)is carried out at a temperature ranging from about 0° C. to about 60° C.7. The process of claim 1 wherein said heating in step b) is carried outat temperatures sufficient to remove residual pore volume water and tofix the incorporated sulfur onto the catalyst.
 8. The process of claim 7wherein said heating in step b) is carried out at temperatures rangingfrom about 50° C. to about 400° C.
 9. The process of claim 1 whereinsaid heating in step b) is carried out in the presence of anon-oxidizing gas selected from the group consisting of nitrogen, carbondioxide, argon, helium and mixtures thereof.
 10. A presulfided catalystcomposition prepared by a process which comprises:(a) impregnating acatalyst containing at least one metal or metal oxide with an inorganicpolysulfide solution such that at least a portion of said sulfide orsulfur is incorporated in the pores of said catalyst; and (b) heatingsaid sulfur-incorporated catalyst in the presence of a non-oxidizingatmosphere to fix the incorporated sulfur onto the catalyst.